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authorJohannes Berg <johannes.berg@intel.com>2020-04-30 22:13:12 +0200
committerDavid S. Miller <davem@davemloft.net>2020-04-30 17:51:42 -0700
commitd07dcf9aadd6b2842b439e8668ff7ea2873f28d7 (patch)
tree65bead82c5e5ff278acbe657226f91c93a58019f /net/netlink/genetlink.c
parent2c28ae48f24d84fcda31fb8acaf2edca6ec46c49 (diff)
downloadlinux-sh-d07dcf9aadd6b2842b439e8668ff7ea2873f28d7.tar.gz
netlink: add infrastructure to expose policies to userspace
Add, and use in generic netlink, helpers to dump out a netlink policy to userspace, including all the range validation data, nested policies etc. This lets userspace discover what the kernel understands. For families/commands other than generic netlink, the helpers need to be used directly in an appropriate command, or we can add some infrastructure (a new netlink family) that those can register their policies with for introspection. I'm not that familiar with non-generic netlink, so that's left out for now. The data exposed to userspace also includes min and max length for binary/string data, I've done that instead of letting the userspace tools figure out whether min/max is intended based on the type so that we can extend this later in the kernel, we might want to just use the range data for example. Because of this, I opted to not directly expose the NLA_* values, even if some of them are already exposed via BPF, as with min/max length we don't need to have different types here for NLA_BINARY/NLA_MIN_LEN/NLA_EXACT_LEN, we just make them all NL_ATTR_TYPE_BINARY with min/max length optionally set. Similarly, we don't really need NLA_MSECS, and perhaps can remove it in the future - but not if we encode it into the userspace API now. It gets mapped to NL_ATTR_TYPE_U64 here. Note that the exposing here corresponds to the strict policy interpretation, and NLA_UNSPEC items are omitted entirely. To get those, change them to NLA_MIN_LEN which behaves in exactly the same way, but is exposed. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink/genetlink.c')
-rw-r--r--net/netlink/genetlink.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 9f357aa22b94..2f049692e012 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1043,6 +1043,80 @@ static int genl_ctrl_event(int event, const struct genl_family *family,
return 0;
}
+static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
+{
+ const struct genl_family *rt;
+ unsigned int fam_id = cb->args[0];
+ int err;
+
+ if (!fam_id) {
+ struct nlattr *tb[CTRL_ATTR_MAX + 1];
+
+ err = genlmsg_parse(cb->nlh, &genl_ctrl, tb,
+ genl_ctrl.maxattr,
+ genl_ctrl.policy, cb->extack);
+ if (err)
+ return err;
+
+ if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
+ return -EINVAL;
+
+ if (tb[CTRL_ATTR_FAMILY_ID]) {
+ fam_id = nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
+ } else {
+ rt = genl_family_find_byname(
+ nla_data(tb[CTRL_ATTR_FAMILY_NAME]));
+ if (!rt)
+ return -ENOENT;
+ fam_id = rt->id;
+ }
+ }
+
+ rt = genl_family_find_byid(fam_id);
+ if (!rt)
+ return -ENOENT;
+
+ if (!rt->policy)
+ return -ENODATA;
+
+ err = netlink_policy_dump_start(rt->policy, rt->maxattr, &cb->args[1]);
+ if (err)
+ return err;
+
+ while (netlink_policy_dump_loop(&cb->args[1])) {
+ void *hdr;
+ struct nlattr *nest;
+
+ hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+ cb->nlh->nlmsg_seq, &genl_ctrl,
+ NLM_F_MULTI, CTRL_CMD_GETPOLICY);
+ if (!hdr)
+ goto nla_put_failure;
+
+ if (nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, rt->id))
+ goto nla_put_failure;
+
+ nest = nla_nest_start(skb, CTRL_ATTR_POLICY);
+ if (!nest)
+ goto nla_put_failure;
+
+ if (netlink_policy_dump_write(skb, cb->args[1]))
+ goto nla_put_failure;
+
+ nla_nest_end(skb, nest);
+
+ genlmsg_end(skb, hdr);
+ continue;
+
+nla_put_failure:
+ genlmsg_cancel(skb, hdr);
+ break;
+ }
+
+ cb->args[0] = fam_id;
+ return skb->len;
+}
+
static const struct genl_ops genl_ctrl_ops[] = {
{
.cmd = CTRL_CMD_GETFAMILY,
@@ -1050,6 +1124,10 @@ static const struct genl_ops genl_ctrl_ops[] = {
.doit = ctrl_getfamily,
.dumpit = ctrl_dumpfamily,
},
+ {
+ .cmd = CTRL_CMD_GETPOLICY,
+ .dumpit = ctrl_dumppolicy,
+ },
};
static const struct genl_multicast_group genl_ctrl_groups[] = {